Method and server for providing notary service for file and verifying file recorded by notary service

ABSTRACT

According to one aspect of the present disclosure, provided is a method for providing a notary service for a file, the method comprising the steps in which: (a) when a notary service request for a specific file is obtained, a server generates, by using a hash function, or supports the generation of, a message digest of the specific file; and (b) if a predetermined condition is satisfied, the server registers, in a database, or supports the registration of, a representative hash value or a value obtained by processing the representative hash value, the representative hash value being generated by calculating at least one neighboring hash value that matches a specific hash value, wherein the specific hash value is a hash value of the result of encrypting the message digest with a private key of a first user, a private key of a second user and a private key of the server.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.16/665,779, filed Oct. 28, 2019, which is a divisional of U.S.application Ser. No. 16/049,379, filed Jul. 30, 2018 (now U.S. Pat. No.10,491,396), which is based on PCT filing PCT/KR2017/001072, filed onFeb. 1, 2017, and claims priority to KR 10-2016-0012763 filed Feb. 2,2016, the entire disclosure of each are incorporated herein byreference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a method for providing a notaryservice for a file and verifying the file recorded by the notaryservice; and more particularly, to the method for providing the notaryservice for the file and verifying the file recorded by using the notaryservice, including a “notary process” of, if a notary service requestfor the file is acquired, generating or supporting another device togenerate a specific message digest of the file by using a specificfunction, and, if one of anchoring conditions is satisfied, registeringor supporting another device to register a first representative value orits processed value in a database, wherein the representative value isgenerated by using a specific value and its corresponding at least oneneighboring value, and wherein the specific value is a function value ofa result acquired by encoding the specific message digest with a privatekey of a specific user and a private key of a server, and a“verification process” of, if a verification request for the file isacquired, and if a second representative value or its processed value,generated by using input data included in the verification request,corresponds to the first representative value or its processed valueregistered in the database, determining or supporting another device todetermine that verification of the file is completed, and the serverusing the same.

BACKGROUND OF THE DISCLOSURE

Authentication is an act of publicly certifying the existence or thecontents of a specific fact or specific legal relations. When theauthentication of the specific legal relations is requested, anauthentication officer generally writes, signs and seals, and stores adocument in an authentication office.

However, there are constraints of time and space, and a possibility ofmissing, forging, and falsifying an authenticated document in aconventional authentication method because a client physically visitsthe authentication office with a document to be authenticated and itscertificate is stored in the authentication office.

Herein, the inventor of the present disclosure developed anauthentication system for a file to perform the authentication inreal-time without a possibility of forgery and falsification and withoutconstraints of space by recording authentication information in ablockchain of virtual currency and filed a patent application, KoreanPatent Application No. 2015-0188978.

However, there are disadvantages such as a bottleneck in providing theservice caused by the increased number of transactions since theauthentication system for the file using the blockchain generates an OPmessage for every file and records it in the blockchain, and high costsfor a service management because the transaction fee must be paid everytime.

Accordingly, there is a need for a technical solution that cancompensate for the disadvantages, thereby guaranteeing a fast serviceand reducing the costs while taking the advantage of the authenticationsystem for the file to perform the authentication in real-time withoutthe possibility of forgery and falsification and without constraints ofspace.

SUMMARY OF THE DISCLOSURE

It is an object of the present disclosure to solve all theaforementioned problems.

It is another object of the present disclosure to guarantee fast servicespeed and reduce a transaction cost, when providing a notary service fora file to perform authentication and verification in real-time byrecording authentication information in a blockchain of virtualcurrency.

It is still another object of the present disclosure to improve servicespeed and reduce the transaction cost, by configuring a specific treeusing information on the notary service and registering only a rootvalue of the specific tree in the blockchain instead of registering allof the information on the notary service in the blockchain.

It is still yet another object of the present disclosure to provideguaranteed integrity of a database by performing the verification usingthe specific tree generated in response to a verification request forthe file.

In accordance with one aspect of the present disclosure, there isprovided a method for providing a notary service for a file, includingsteps of: (a) a server, if a notary service request for the file isacquired, generating or supporting another device to generate a specificmessage digest of the file by using a specific function; and (b) theserver, if one of anchoring conditions is satisfied, registering orsupporting another device to register a representative value or itsprocessed value in a database, wherein the representative value isgenerated by using a specific value and its corresponding at least oneneighboring value, and wherein the specific value is a function value ofa result acquired by encoding the specific message digest with a privatekey of a first user, a private key of a second user, and a private keyof the server.

In accordance with another aspect of the present disclosure, there isprovided a method for verifying a file recorded by using a notaryservice, including steps of: (a) a server acquiring or supportinganother device to acquire a verification request for the file, oncondition that the server has acquired a notary service request for thefile, and then has registered a first representative value or itsprocessed value in a database, wherein the first representative value isgenerated by using a first specific value and its corresponding at leastone neighboring value under one of anchoring conditions, and wherein thefirst specific value is a function value of a result acquired byencoding a specific message digest of the file with a private key of afirst user, a private key of a second user, and a private key of theserver; and (b) the server, if a second representative value or itsprocessed value, generated by using input data included in theverification request, corresponds to the first representative value orits processed value registered in the database, determining orsupporting another device to determine that a verification of the fileis completed.

In accordance with still another aspect of the present disclosure, thereis provided a server for providing a notary service for a file,including: a communication part for acquiring or supporting anotherdevice to acquire a notary service request; and a processor for (I), ifthe notary service request for the file is acquired, generating orsupporting another device to generate a specific message digest of thefile by using a specific function, and (II), if one of anchoringconditions is satisfied, registering or supporting another device toregister a representative value or its processed value in a database,wherein the representative value is generated by using a specific valueand its corresponding at least one neighboring value, and wherein thespecific value is a function value of a result acquired by encoding thespecific message digest with a private key of a first user, a privatekey of a second user, and a private key of the server.

In accordance with still yet another aspect of the present disclosure,there is provided a server for verifying a file recorded by using anotary service, including: a communication part for acquiring orsupporting another device to acquire a verification request for thefile; and a processor for, on condition that the server has acquired anotary service request for the file, and then has registered a firstrepresentative value or its processed value in a database, wherein thefirst representative value is generated by using a first specific valueand its corresponding at least one neighboring value under one ofanchoring conditions, and wherein the first specific value is a functionvalue of a result acquired by encoding a specific message digest of thefile with a private key of a first user, a private key of a second user,and a private key of the server, if the verification request isacquired, and if a second representative value or its processed value,generated by using input data included in the verification request,corresponds to the first representative value or its processed valueregistered in the database, determining or supporting another device todetermine that a verification of the file is completed.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings attached below to explain example embodiments of thepresent disclosure are only part of example embodiments of the presentdisclosure and other drawings may be obtained based on the drawingswithout inventive work for those skilled in the art:

FIG. 1 is a block diagram illustrating a configuration of a server thatprovides a notary service for a file and verifies the file recorded byusing the notary service, in accordance with one example embodiment ofthe present disclosure.

FIG. 2 is a sequence diagram illustrating a process of performing thenotary service for the file in response to a request from a single user.

FIGS. 3 and 4 are diagrams illustrating examples of specific trees,e.g., Merkle trees generated in accordance with one example embodimentof the present disclosure.

FIG. 5 is a sequence diagram illustrating a process of performing averification service for the file in response to a request from a singleuser.

FIG. 6 is a sequence diagram illustrating a parallel signing process ofperforming in parallel the notary service in response to notary servicerequests from multiple users.

FIG. 7 is a sequence diagram illustrating a serial signing process ofperforming the notary service sequentially in response to notary servicerequests from multiple users.

FIG. 8 is a sequence diagram illustrating a process of performingverification for the file authenticated with signings of the multipleusers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings that show, by way of illustration, specificembodiments in which the disclosure may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the disclosure. It is to be understood that the variousembodiments of the present disclosure, although different, are notnecessarily mutually exclusive. For example, a particular feature,structure, or characteristic described herein in connection with oneembodiment may be implemented within other embodiments without departingfrom the spirit and scope of the present disclosure. In addition, it isto be understood that the position or arrangement of individual elementswithin each disclosed embodiment may be modified without departing fromthe spirit and scope of the present disclosure. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present disclosure is defined only by the appended claims,appropriately interpreted, along with the full range of equivalents towhich the claims are entitled. In the drawings, like numerals refer tothe same or similar functionality throughout the several views.

FIG. 1 is a block diagram illustrating a configuration of a server thatprovides a notary service for a file and verifies the file recorded byusing the notary service, in accordance with one example embodiment ofthe present disclosure. And FIG. 2 is a sequence diagram illustrating aprocess of performing the notary service for the file in response to arequest from a single user.

Before explaining each of example embodiments, the following aredefinitions of expressions used in the present specification. On theleft of ‘:’ is an expression and on the right is a definition of theexpression.

Definitions of Expressions

PrivX: Private key of X

PubX: Public key of X

AESX: AES secret key of X

Enc_(PrivX)(Y): Output of encryption of Y using PrivX

Dec_(PubX)(Y): Output of decryption of Y using PubX

Enc_(AESX)(Y): Output of AES encryption of Y using AESX

Dec_(AESX)(Y): Output of AES decryption of Y using AESX

Hash(Y): Hash value of Y

First of all, a process of performing the notary service for the file inresponse to the request from the single user is explained by referringto FIGS. 1 and 2.

By referring to FIG. 1, the server 100 that performs the notary servicefor the file in accordance with said one example embodiment of thepresent disclosure may include a communication part 110 and a processor120. The server in each example embodiment may be a separate server, butfor convenience, it is explained that the service is performed by thesingle server 100. In addition, the server may further include a memorycapable of storing computer readable instructions for performingfollowing processes. As one example, the processor, the memory, amedium, etc. may be integrated with an integrated processor.

The communication part 110 may be configured to transmit and receivedata to and from the user or a user device, and a database 200. First,the communication part 110 may acquire or support another device toacquire a notary service request for the file at a step of S210. Asillustrated in FIG. 2, if the notary service request for the file isacquired, the file and PubU, which is a public key of the user whorequests the notary service, may be acquired. The communication part 110may respond to the request at a step of S220 where the request and itscorresponding response may be performed during one TCP session.

If the notary service request for the file is acquired, the processor120 may generate or support another device to generate a message digestof the file using a specific function, e.g., a hash function, at a stepof S215, that is, the message digest may be represented byMD=Hash(File). Herein, the specific function may be the hash functionwhich may vary in its type. For example, the hash function may be triplesha256. Also, the hash function in the present specification generallymeans a function to transform the original file, but may include afunction that just stores the file without any modification in anextreme case. In this case, the message digest generated by using thehash function may be the same as the file.

The message digest generated in response to the notary service requestfor the file at the step of S220 may be transmitted to the user whorequests the notary service for the file. If the user requests thenotary service through the user device, not shown in the diagram, thegenerated message digest may be transmitted to the user device.

Next, the communication part 110 may acquire EncPrivU(MD), calculated byencoding the message digest with a private key PrivU of the user, fromthe user at a step of S225. In this case, the message digest and thePubU may also be received from the user because the TCP session may bedisconnected after the response of the step S220. For reference,although the present specification is described by using expressionsEncPriv(MD) and EncPub(MD) of encoding the message digest with a privatekey and a public key, the expressions may be replaced with SigPriv(File)and SigPub(File). Additionally, in case that the message digest isgenerated more than once, expressions SigPriv(MD) and SigPub(MD) may beused.

Further, if the EncPrivU(MD), calculated by encoding the message digestwith the PrivU, is acquired, and if the generated message digest Bcorresponds to information A which is DecPubU(EncPrivU(MD)) acquired bydecoding the EncPrivU(MD) with the PubU at a step of S230-2, theprocessor 120 may generate or support another device to generate afunction value of a first encoded message digest generated by encodingthe message digest with the PrivU and a private key PrivC of the server100 using the specific function at a step of S240, and may register orsupport another device to register the generated function value of thefirst encoded message digest in the database 200 at a step of S250.Herein, the function value may be a hash value, but the presentdisclosure is not limited thereto. The reason for registering themessage digest in the form of a function value in the database 200 isthat the size of the data needs to be reduced due to the limits on astorage capacity of the database 200. Herein, the database 200 may be ablockchain of virtual currency, i.e., cryptocurrency. For example, itmay be a bitcoin blockchain.

For reference, in the FIG. 2, the expression ‘DecPubU(EncPrivU(MD))==MD’is used to represent that the A corresponds to the B, but the expressionof the present disclosure is not limited thereto. For example,‘True==VerPubU(SigPrivU(File))’ may also represent the samerelationship. Additionally, in case that the message digest is generatedmore than once, the expression ‘True VerPubU(SigPrivU(MD))’ may be used.

Moreover, if the A corresponds to the B, the processor 120 may registeror support another device to register the function value of the firstencoded message digest, for example, Hash[EncPrivC(EncPrivU(MD))] whichis the hash value of the first encoded message digest generated byencoding the message digest in sequence with the PrivU and the PrivC, inthe database 200. In other words, the function value of the firstencoded message digest may be registered in the database 200 after theuser, who is a client, signs the message digest first with the PrivU andthen the server 100, which is an authentication officer, signs it withthe PrivC. However, the order of signing may be different from this.Especially, if a session between the user and the server 100 is beingmaintained, the server 100 may sign first and then the user may.

In case that the function value of the first encoded message digestgenerated by encoding the message digest with the PrivU and the PrivC isregistered in the database 200, the communication part 110 may acquire atransaction ID, i.e., TxID, from the database 200 at a step of S255,wherein the TxID indicates a location of the function value of the firstencoded message digest registered in the database 200.

On the other hand, if the A does not correspond to the B at a step of230-1, the processor 120 may send a message of unsuccessful registrationto the user by reason that the user is not a person related to the file,e.g. a transactor, at a step of S235.

Additionally, if the A corresponds to the B, the processor 120 may storeor support another device to store the file at a step of S245. Herein,the file may be encrypted with a symmetric key encryption algorithm suchas AES, i.e., Advanced Encryption Standard. In this case, the secret keymay be a certain secret key processed from the public key of the user,but the scope of the present disclosure is not limited thereto.

The processor 120 may store or support another device to store the PubU,the message digest MD, the EncPrivU(MD), and the TxID. Moreover, theprocessor 120 may further store or support another device to storeEncPrivC(EncPrivU(MD)), which is the first encoded message digestgenerated by encoding the MD in sequence with the PrivU and the PrivC,and its function value, for example, its hash valueHash[EncPrivC(EncPrivU(MD))].

If authentication information is registered in the database 200 asstated above, the communication part 110 may send a message ofsuccessful registration to the user at a step of S260.

However, in case of the aforementioned example embodiment, there aredisadvantages such as a bottleneck in providing the service caused bythe increased number of transaction requests because an OP message isgenerated for every file and recorded in the blockchain, and high costsfor a service management because the transaction fee must be paid everytime.

Hereinafter, an authentication system is explained that can takeadvantage of and further complement the authentication system for thefile to perform the authentication in real-time without a possibility offorgery and falsification, thereby guaranteeing a fast service andreducing the costs while. Such an authentication system uses a distinctdata structure managed by the server 100, unlike the aforementionedexample embodiment.

If the notary service request for the file is acquired through thecommunication part 110, the aforementioned processor 120 may generate orsupport another device to generate a specific message digest of the fileusing the specific function, e.g., the hash function. The repeatedexplanation is omitted as it is similar to the aforementioned exampleembodiment. Herein, the notary service for the file may be anauthentication service for the file or a revocation service for thefile, unlike the aforementioned example embodiment.

Also, if one of anchoring conditions is satisfied, the processor 120 mayregister or support another device to register a representative value orits processed value in a database, wherein the representative value isgenerated by using a specific value and its corresponding at least oneneighboring value, and wherein the specific value is a function value ofa result acquired by encoding the specific message digest with a privatekey of a specific user and the private key of the server 100 using thespecific function. In other words, the processor 120, if said one of theanchoring conditions is satisfied, may generate or support anotherdevice to generate the representative value or its processed value bycalculating the function value of the result and its corresponding atleast one neighboring value, acquired by encoding the specific messagedigest with the private key PrivU of the specific user and the privatekey PrivC of the server 100, and register or support another device toregister the generated representative value or its processed value inthe database, instead of registering the function value of the result ofencoding the specific message digest with the PrivU and the PrivC asstated above at the step of S240. Herein, the database may not bemanaged by the server 100 like the aforementioned database 200, e.g. theblockchain of the virtual currency, but may also be managed by theserver 100. The explanation in the present specification is focused onthe database 200 which is not managed by the server 100, but thetechnical idea of the present disclosure may be applied to the databasemanaged by the server 100.

The calculation of the specific value and its corresponding at least oneneighboring value may be performed by various functions. Assuming thespecific value to be input and the neighboring values to be x1, x2, . .. , and xn, the representative value t may be expressed, for example, asthe following equation.t=hash(function(input,x1,x2, . . . ,xn))  <Equation>

Herein, the server 100 may store or support another device to store thespecific value and its corresponding at least one neighboring value in acertain form of a data structure and manage them. In this regard, thedata structure may vary, and one example thereof may be a structure of aspecific tree. In this case, the calculation of the specific value andits corresponding at least one neighboring value may be performed byusing the specific tree. Herein, the specific tree may be at least oneMerkle tree, but the scope of the present disclosure is not limitedthereto.

In other words, the processor 120 may generate or support another deviceto generate at least one specific tree including a specific leaf nodewhere the specific value is allocated, and if said one of the anchoringconditions is satisfied, may register or support another device toregister the representative value or its processed value, which iscalculated from the specific value and at least one function valueallocated to at least one of other leaf nodes which have same depth asthe specific leaf node, in the database 200. Herein, the representativevalue may represent a value in a root node of the specific tree or avalue in an intermediate node of the specific tree, but the scope of thepresent disclosure is not limited thereto.

More specifically, in case that the specific tree is a Merkle tree, (x1)the processor 120 may calculate or support another device to calculate(i) a specific hash value and (ii) a hash value allocated to a siblingnode of the specific leaf node where the specific hash value isallocated, to thereby acquire a resultant value, and then allocate orsupport another device to allocate a hash value of the resultant valueto a parent node of the specific leaf node. (x2) If the parent node is aroot node of the Merkle tree, the hash value of the resultant valueallocated to the parent node may be regarded as a representative hashvalue. (x3) On the other hand, if the parent node is not the root nodeof the Merkle tree, the processor 120 may repeat or support anotherdevice to repeat the steps of (x1) to (x3) by using the hash valueallocated to the parent node as the specific hash value.

Additionally, the processor 120 may register or support another deviceto register the hash value ultimately allocated to the root node or theparent node of the Merkle tree in the database 200 as the representativevalue. Herein, the processed value of the representative value may beregistered. For example, a value resulting from hex operation on therepresentative value may be registered.

A first data structure and a second data structure may be linked in aform of a chain if the server 100 stores the specific value and the atleast one neighboring value in the first data structure and then storesand manages the second data structure in an identical form with thefirst data structure. Hereinafter, the representative value is assumedto represent a value in a root node of the Merkle tree.

As stated above, if the first data structure and the second datastructure are the structure of the Merkle tree, a root value of thefirst data structure or its processed value may be allocated to a firstleaf node of the second data structure.

Moreover, data integrity may be further ensured by verifying the firstdata structure when the second data structure is generated. Verificationof the second data structure will be explained later.

Further, in case of a first specific tree among two or more specifictrees linked in a form of a chain, a function value of certain messagedata or its processed value comprised of text, number or symbol may beallocated to a first leaf node of the first specific tree. For example,a function value of a first input message given by the server 100 at thetime of generation of the specific tree may be allocated.

FIGS. 3 and 4 are diagrams illustrating examples of the specific trees,i.e., the Merkle trees, generated in accordance with said one exampleembodiment of the present disclosure.

FIG. 3 illustrates a Merkle tree with four (2²) leaf nodes. As theillustrated Merkle tree is the first Merkle tree whose tree_id is zero,the hash value triplesha256digest(coinplug_unique_message) of thecertain message data “Coinplug 2016-01-01” is allocated to a node h0which is the first leaf node. In case that the notary service requestfor the file is acquired, the processor 120 may generate or supportanother device to generate a leaf node next to the last leaf node of thecurrently configured Merkle tree and allocate or support another deviceto allocate the specific hash value or its processed value to thegenerated leaf node. For example, if allocation is completed up to anode h1, which is a second leaf node of the Merkle tree in FIG. 3, at aprevious step, a node h2 which is a next leaf node may be generated andthe specific hash value or its processed valuetriplesha256digest(input2) may be allocated to the node h2. Further, theprocessor 120 may calculate or support another device to calculate (i)the specific hash value and (ii) a hash value allocated to a siblingnode h3 of the node h2, which is a third leaf node where the specifichash value is allocated to, to thereby acquire a resultant value. A hashvalue of the resultant value may be allocated to a parent node h23 ofthe node h2 and the node h3. As the parent node h23 is not the root nodeof the Merkle tree, the processor 110 may repeat or support anotherdevice to repeat the above process by using the hash value allocated tothe node h23 as the specific hash value. In other words, the hash valueallocated to the node h23 and a hash value allocated to a node h01 maybe used to generate a calculated value which is allocated to a nodeh0123, i.e., a parent node of the node h23 and the node h01. Herein, asthe node h0123 is the root node of the Merkle tree, the processor 120may register or support another device to register a processed valuehex(h{node index}) of the hash value allocated to the node h0123 in thedatabase 200. Additionally, the processor 120 may register or supportanother device to register a processed value hex of the hash valueallocated to at least one of parent nodes of the Merkle tree in thedatabase 200.

Meanwhile, the aforementioned anchoring conditions may include at leastone of (i) acquisition of a certain number of message digests includingthe specific message digest in response to respective notary servicerequests, (ii) a certain time lapse, (iii) generation of a block in ablockchain, and (iv) one or more characteristics of the user whorequests the notary service.

For example, if the message digests are acquired as much as the numberof leaf nodes of the Merkle tree in response to the respective notaryservice requests, a hash value of a result acquired by encoding each ofthe message digests with the private key of each user and the privatekey of the server 100 may be input of the Merkle tree, that is, valuesallocated to the leaf nodes.

Also, the processor 120 may generate or support another device togenerate a root value of the Merkle tree by the certain time as thecondition (ii) above. In this case, if the certain time is elapsed, theprocessor 120 may generate or support another device to generate theMerkle tree using the input of the certain time and may register orsupport another device to register the root value of the Merkle tree inthe database 200.

However, in this case, there may be no value allocated to the siblingnode of the specific leaf node where the specific hash value isallocated despite the certain time lapse. In case that no hash value isallocated to the sibling node of the specific leaf node despite thecertain time lapse, the processor 120 may allocate or support anotherdevice to allocate a certain hash value to the sibling node to therebyproduce the root value of the Merkle tree in the aforementioned way. Forexample, the processor 120 may copy and allocate the specific hash valueto the sibling node.

The characteristics of the user who requests the notary service may beat least part of information on cost paid by the user who requests thenotary service, information on a time-zone during which the notaryservice is performed, information on location where the notary serviceis performed, and information on a type of the user who requests thenotary service. But the scope of the present disclosure is not limitedthereto.

Meanwhile, if generation of a new Merkle tree starts and if said one ofthe anchoring conditions is satisfied without any notary servicerequest, the processor 120 may generate or support another device togenerate the new Merkle tree with first and second leaf nodes wherecertain message data is respectively allocated, and may register orsupport another device to register a root value or its processed valueof the new Merkle tree in the database 200. In this case, the Merkletree may be generated with two leaf nodes.

However, if the server 100 stores the specific hash value and the atleast one neighboring hash value in the first data structure and thenstores and manages the second data structure in an identical form withthe first data structure as aforementioned, the first data structure andthe second data structure may be linked in a form of a chain.Especially, if the first data structure and the second data structureare the Merkle trees, the root value of the first data structure or ahash value of the root value may be allocated to the first leaf node ofthe second data structure.

FIG. 4 is a diagram illustrating an example of a new Merkle treegenerated as the second data structure in accordance with said oneexample embodiment of the present disclosure.

By referring to FIG. 4, it is clear that the root value hex(h0123) ofthe Merkle tree whose tree_id is zero in FIG. 3 is allocated to a nodeh4, which is a first leaf of the new Merkle tree, astriplesha256digest(input4). In such a manner, tracking becomes easiereven in the case of data forgery and, therefore the present disclosurehas an advantage of improving the data integrity, by linking multipledata structures created when a transaction occurs.

Next, a process for verifying a file in response to a request from asingle user is explained.

Verification in the present specification may be requested by thetransactor or a third party, and may be sorted into a case using thedistinct data structure managed by the server 100 and a case withoutusing the distinct data structure. Both terms of “audit” and“verification” may be used. First of all, the verification performedwithout using the distinct data structure managed by the server 100 isexplained.

The file may be verified by a separate device which may refer toinformation on the aforementioned server 100, or by the aforementionedserver 100. Hereinafter, the explanation is based on the verification ofthe file by the aforementioned server 100 for convenience.

FIG. 5 is a sequence diagram illustrating a process of performing averification service for the file in response to the request from thesingle user.

By referring to FIG. 5, similarly to the aforementioned example, thecommunication part 110 may acquire a verification request for the fileat a step of S510. As illustrated in FIG. 5, if the verification requestfor the file is acquired, the file and the PubU, which is the public keyof the user who requests the verification, may be acquired. Thecommunication part 110 may respond to the request, and the request andits corresponding response may be performed within one TCP session.

As stated above, on condition that the server 100 has determined theuser, who requested the notary service of the file, as related to thefile in response to the notary service request for the file and, as aresult, that the server 100 has stored the function value of the firstencoded message digest, generated by encoding the message digest of thefile with the PrivU and the PrivC, in the database 200, and has beenmanaging its corresponding transaction ID, if the verification requestfor the file is acquired, the processor 120 may acquire or supportanother device to acquire the transaction ID corresponding to at leastone of the PubU and the message digest of the file. In this case, thetransaction ID, i.e., TxID, may have been stored in the server 100 or ina device which the server 100 may refer to.

In case that the communication part 110 receives the verificationrequest for the file at the step of S510, if the file is acquired forthe verification, the processor 120 may generate or support anotherdevice to generate an original message digest of the file using the hashfunction, i.e., MD=Hash(File), at a step of S515. In this case, theprocessor 120 may refer to the transaction ID corresponding to at leastone of the PubU and the generated original message digest of the file.

If no information corresponding to the original message digest is founddespite the verification request at a step of S520-1, the communicationpart 110 may send a message of unsuccessful verification to the user ata step of S525.

Also, if the information, which is the transaction ID corresponding tothe original message digest, is found at a step of S520-2, thecommunication part 110 may send a query to the database 200 using theTxID at a step of S525 and acquire an OP message including the functionvalue of the first encoded message digest generated by encoding themessage digest with the PrivU and the PrivC from the database 200 at astep of S530.

Further, if a function value of a second encoded message digest,generated by encoding the original message digest with the PrivC and thePrivU, corresponds to the function value of the first encoded messagedigest in the OP message, then the processor 120 may determine orsupport another device to determine the file as verified at a step ofS535.

Herein, the second encoded message digest generated by encoding theoriginal message digest with the PrivC and the PrivU may beEncPrivC(EncPrivU(MD)) which is generated by encoding the originalmessage digest in sequence with the PrivU and the PrivC.

However, even in case that the function value of X, which is the secondencoded message digest, corresponds to the function value of the firstencoded message digest in the OP message, if a result valueDecPubU(DecPubC(EncPrivC(EncPrivU(MD)))), acquired by decoding the Xwith a public key PubC of the server 100 and the PubU, corresponds tothe message digest of the file, the processor 120 may further determineor support another device to determine the file as verified at a step ofS540. In other words, the verification of the file may be completed withtwo more steps. This is because there may be a possibility of changes inthe private key, the public key, etc. of the user.

The three steps of the verification above may be represented as theexpressions below.OP_MESSAGE==Hash[Enc _(PrivC)(Enc _(PrivU)(MD))]Enc _(PrivU)(MD)==Dec _(PubC)[Enc _(PrivC)(Enc _(PrivU)(MD))]MD(=Hash[File])==Dec _(PubU)[Enc _(PrivU)(MD)]  <Expression 1>

If the verification of the file is successful, the communication part110 may send a message of successful verification to the user at a stepof S545.

Also, if the file is determined as verified, the processor 120 may allowa download of the file. In this case, the user may download the filethrough the user device, etc.

Next, the verification performed by using the distinct data structuremanaged by the server 100 is explained.

First of all, as stated above, on condition that the server 100 hasacquired the notary service request for the file, and then hasregistered the aforementioned representative value, referred to here forconvenience as a first representative value, or its processed value inthe database 200, wherein the first representative value is generated byusing the aforementioned specific value, referred to here forconvenience as a first specific value, and its corresponding at leastone neighboring value under said one of the anchoring conditions, andwherein the first specific value is the function value of the resultacquired by encoding the specific message digest of the file with theprivate key of the specific user and the private key of the server 100,if a verification request for the file is acquired, and if a secondrepresentative value or its processed value, generated by using inputdata included in the verification request, corresponds to the firstrepresentative value or its processed value registered in the database200, then the processor 120 may determine or support another device todetermine that the verification of the file is completed.

In this regard, the second representative value may be generated bycalculating a second specific value and its corresponding at least oneneighboring value, wherein the second specific value is a function valueof a result acquired by encoding the specific message digest of the fileextracted from the input data included in the verification request withthe private key of the specific user and the private key of the server.

Herein, the input data included in the verification request may have atleast one of (i) the file, (ii) the specific message digest of the file,or (iii) an ID issued during the notary service for the file.

If the input data includes the file, the specific message digest of thefile may be generated by the aforementioned method, and the secondspecific value may be generated based thereon. Further, the secondrepresentative value may be generated by calculating the second specificvalue and its corresponding at least one neighboring value.

If the input data includes the ID issued during the notary service, thesecond specific value may be set to a value allocated to a leaf nodecorresponding to the ID in the previously generated specific tree. Inthe examples illustrated in FIGS. 3 and 4, the ID may be a unique ID.

The same explanation for the first specific value aforementioned may beapplied to the second specific value. That is, the calculation of thesecond specific value and its corresponding at least one neighboringvalue may be performed by various functions. Thus the explanationthereof is omitted by referring to the above.

In this case, the calculation of the second specific value and itscorresponding at least one neighboring value may be performed by using aspecific tree. If the verification request is acquired, the processor120 may identify or support another device to identify information onthe specific tree related to the input data and on its leaf nodes.

Further, the second representative value may be calculated by using thesecond specific value allocated to a specific leaf node of the specifictree.

In case that the service is performed by using the database not managedby the server 100, e.g. the blockchain of the virtual currency, theprocessor 120 may refer or support another device to refer to a certaintransaction ID corresponding to the information on the identifiedspecific tree.

In this case, if the verification request for the file is acquired, theprocessor 120 may refer or support another device to refer to thecertain transaction ID, and acquire or support another device to acquirean OP message from the database 200 by referring to the certaintransaction ID. Also, if the second representative value or itsprocessed value, generated by using the input data included in theverification request, corresponds to the first representative value orits processed value included in the OP message, the verification of thefile may be determined as completed.

Meanwhile, the certain transaction ID may be provided as included in theinput data. In other words, in response to the verification request, theuser may transmit or support another device to transmit the certaintransaction ID to the server 100 in addition to at least one of (i) thefile, (ii) the specific message digest of the file, or (iii) the IDissued during the notary service for the file.

In a calculation process of the verification, the processor 120 maygenerate or support another device to generate a new specific tree. Inthis process, the specific tree generated during the aforementionednotary service may be used. For example, in case of a Merkle tree, (x1)the processor 120 may calculate or support another device to calculate(i) the second specific hash value and (ii) a hash value allocated to asibling node of the specific leaf node where the second specific hashvalue is allocated in the previously generated Merkle tree, to therebyacquire a resultant value, and then allocate or support another deviceto allocate a hash value of the resultant value to a parent node of thespecific leaf node in the new Merkle tree. Further, (x2) if the parentnode is a root node of the new Merkle tree, the processor 120 maycompare or support another device to compare the hash value allocated tothe parent node, as the second representative hash value, with the firstrepresentative hash value or its processed value included in the OPmessage, and (x3) if the parent node is not the root node of the Merkletree, repeat or support another device to repeat the steps of (x1) to(x3) by using the hash value allocated to the parent node as the secondspecific hash value.

If the root value or its processed value ultimately generated in thespecific tree corresponds to the first representative value or itsprocessed value in the OP message, the processor 120 may determine orsupport another device to determine that the verification of the file iscompleted.

In the present disclosure, if a specific tree with n^(m)(=N) leaf nodesis generated during the notary service, integrity of the transaction maybe confirmed quickly as the verification of the file is possible bycalculating only as much as the height of the specific tree, i.e.,log_(n) N=m.

On the other hand, if the input data is acquired, the processor 120 mayidentify or support another device to identify at least part of theinformation on the specific tree related to the input data and on itsleaf nodes, by referring to time information related to the input data.

Hereinafter, the verification process is explained by taking an exampleillustrated in FIG. 3.

By referring to FIG. 3 again, if verification of input 2 is requested,the processor 120 may identify or support another device to identify theinformation on the previously generated Merkle tree and on its leafnodes by referring to the information on the input data, and acquire orsupport another device to acquire the OP message from the database 200by transmitting the certain transaction ID corresponding to theinformation on the identified Merkle tree whose tree_id is zero to thedatabase 200. Then, the processor 120 may generate or support anotherdevice to generate the new Merkle tree by using the input 2. As a hashvalue of the input 2, i.e., triplesha256digest(input2), is allocated tothe node h2, the processor 120 may calculate or support another deviceto calculate the hash value allocated to the node h2 and the hash valueallocated to the sibling node h3 of the node 2 in the previouslygenerated Merkle tree, to thereby acquire a resultant value. A hashvalue of the resultant value may be allocated to the parent node h23 ofthe node h2 and the node h3. As the node h23 is not the root node of thenew Merkle tree, the processor 120 may repeat or support another deviceto repeat the above process by using the hash value allocated to thenode 23 as the second specific hash value. In other words, by using thehash value allocated to the node h23 as the second specific hash value,the hash value allocated to the node h23 and the hash value allocated tothe node h01 in the previously generated Merkle tree may be calculatedand then allocated to the node h0123 which is the parent node of thenode h23 and the node h01. Herein, as the node h0123 is the root node ofthe Merkle tree, the processor 120 may compare or support another deviceto compare the processed value hex(h{node index}) of the hash valueallocated to the node h0123 with the first representative hash value orits processed value included in the OP message.

Next, a process for performing the notary service of the file inresponse to requests from multiple users is explained in accordance withanother example embodiment of the present disclosure. However, therepeated explanation is omitted. Further, the same numerals indicate thesame devices in the previous embodiment of the present disclosure. Firstof all, an authentication system without using the distinct datastructure managed by the server 100 is explained.

FIG. 6 represents a parallel signing process of performing the notaryservices in parallel, and FIG. 7 represents a serial signing process ofperforming the notary services sequentially, in response to the notaryservice requests from at least part of the multiple users.

First of all, by referring to FIG. 6, if at least two notary servicerequests for the file are acquired from at least two of the multipleusers at steps of S610 and S620, the processor 120 may generate orsupport another device to generate the message digest MD=Hash(File) ofthe file using the specific function, e.g., the hash function, at eachstep of S612 and S622. Moreover, if a first message digest generated byencoding the message digest with a private key PrivU1 of a first userand a second message digest generated by encoding the message digestwith a private key PrivU2 of a second user are acquired at steps of S640and S650, and if each piece of (i) information A′ which isDecPubU1(EncPrivU1(MD)) acquired by decoding the first message digestwith a public key PubU1 of the first user and (ii) information B′ whichis DecPubU2(EncPrivU2(MD)) acquired by decoding the second messagedigest with a public key PubU2 of the second user corresponds to thegenerated message digest C′, which is the MD, at a step of S640-3, thenthe processor 120 may register or support another device to register afunction value of a third message digest, generated by encoding the MDwith the PrivU1, the PrivU2, and the PrivC, in the database 200 at astep of S675.

Next, the communication part 110 may acquire a transaction ID indicatinga location of the registered function value of the third message digestin the database 200 at a step of S680.

Moreover, if each of the A′ and the B′ corresponds to the C′, theprocessor 120 may register or support another device to registerEncPrivC(EncPrivU1(MD)+EncPrivU2(MD)), which is acquired by encoding adata group with the PrivC, in the database 200, wherein the data groupis comprised of the first message digest generated by encoding the MDwith the PrivU1 and the second message digest generated by encoding theMD with the PrivU2.

Next, by referring to FIG. 7, if the notary service request for the fileis acquired at each step of S710 and S735, the processor 120 maygenerate or support another device to generate the message digestMD=Hash(File) of the file using the specific function, e.g., the hashfunction, at each step S712 and S737. In this case, as illustrated inFIG. 7, the PubU1, the PubU2, and the file may be acquired together.

If (i) the first message digest EncPrivU1(MD), generated by encoding themessage digest with the PrivU1, is acquired at a step of S720, andinformation A″, which is the DecPubU1(EncPrivU1(MD)) acquired bydecoding the first message digest with the PubU1, corresponds to thegenerated message digest B″, which is the MD, and if (ii)EncPrivU2(EncPrivU1(MD)), generated by encoding the message digest withthe PrivU1 and the PrivU2, is acquired at a step of S745, andinformation C″ which is DecPubU2(EncPrivU2(EncPrivU1(MD))) acquired bydecoding the EncPrivU2(EncPrivU1(MD)) with the PubU2 corresponds toinformation D″ which is the first message digest EncPrivU1(MD) at a stepof S760, then the processor 120 may register or support another deviceto register the function value of the third message digest, generated byencoding the message digest with the PrivU1, the PrivU2, and the PrivC,in the database 200 at a step of S775.

Moreover, if the A″ corresponds to the B″, and if the C″ corresponds tothe D″, the processor 120 may register or support another device toregister SO=EncPrivC(EncPrivU2(EncPrivU1(MD))), which is generated byencoding the message digest in sequence with the PrivU1, the PrivU2, andthe PrivC, in the database 200.

Herein, the communication part 110 may acquire the transaction ID, i.e.,TxID, indicating a location of the registered function value of thethird message digest in the database 200 at a step of S780.

Next, said another example embodiment of responding to the notaryservice requests from the multiple users in the authentication systemusing the distinct data structure managed by the server 100 is furtherexplained.

The processor 120, (i) if the notary service request for the file isacquired, may generate or support another device to generate thespecific message digest of the file by using the specific function, and,(ii) if one of the anchoring conditions is satisfied, may register orsupport another device to register a representative value or itsprocessed value in the database 200, wherein the representative value isgenerated by using the specific value and its corresponding at least oneneighboring value, and wherein the specific value is a function value ofa result acquired by encoding the specific message digest with theprivate key of the first user, the private key of the second user, andthe private key of the server 100.

Herein, in the parallel signing process, the specific value may be afunction value of EncPrivC(EncPrivU1(MD)+EncPrivU2(MD)), which isacquired by encoding a data group with the private key of the server100, wherein the data group is comprised of a first encoded messagedigest generated by encoding the specific message digest with theprivate key of the first user and a second encoded message digestgenerated by encoding the specific message digest with the private keyof the second user.

On the other hand, in the serial signing process, the specific value maybe a function value of EncPrivC(EncPrivU2(EncPrivU1(MD))), which isacquired by encoding the specific message digest in sequence with theprivate key of the first user, the private key of the second user, andthe private key of the server 100.

Next, a process for verifying the authenticated file in response torequests from multiple users is explained. First of all, verificationperformed without using the distinct data structure managed by theserver 100 is explained by referring to FIG. 8. However, the repeatedexplanation is omitted.

FIG. 8 is a sequence diagram illustrating the process for verifying thefile authenticated with signings of the multiple users.

For reference, steps of S825 to S850 represent a serial signing processfor verifying the file sequentially, and steps of S860 to S885 representa parallel signing process for verifying the file in parallel, inresponse to verification requests from at least part of the multipleusers. Both the serial signing process and the parallel process can beapplied to a service provided by the present disclosure.

By referring to FIG. 8, as stated above, on condition that the server100 has determined the first user and the second user as related to thefile in response to the notary service requests for the file, and as aresult, that the server 100 has stored the function value of the thirdmessage digest, generated by encoding the MD of the file with thePrivU1, the PrivU2, and the PrivC, in the database 200, and that theserver 100 has been managing its corresponding transaction ID, i.e.,TxID, if at least one of the verification requests for the file isacquired at a step of S810, the processor 120 may acquire the TxIDcorresponding to at least one of an original message digest of the file,for example, MD=Hash(File), and the public keys of the users whorequests the verification of the file.

Also, the communication part 110 may acquire an OP message, whichincludes the function value of the third message digest from thedatabase 200 by referring to the TxID at each step of S835 and S870.

Further, if a function value of a fourth message digest generated byencoding the original message digest with the PrivC, the PrivU1, and thePrivU2 correspond to the function value of the third message digest inthe OP message, then the processor 120 may determine or support anotherdevice to determine the file as verified at each step of S840 and S875.

In the parallel signing process, the processor 120 may determine orsupport another device to determine the file as verified according towhether the function value, for example,Hash[EncPrivC(EncPrivU1(MD)+EncPrivU2(MD))], which is a function valueof a first encoded value acquired by encoding a data group with thePrivC, corresponds to the function value of the third message digest inthe OP message, wherein the data group is comprised of a fifth messagedigest generated by encoding the original message digest with the PrivU1and a sixth message digest generated by encoding the original messagedigest with the PrivU2.

However, even in case that the function value, e.g., the hash valueHash[EncPrivC(EncPrivU1(MD)+EncPrivU2(MD))] of Y, which is the firstencoded value acquired by encoding the data group comprised of the fifthmessage digest and the sixth message digest with the PrivC, correspondsto the function value of the third message digest, generated by encodingthe message digest with the PrivU1, the PrivU2, and the PrivC, in the OPmessage, if (i) a first decoded value obtained by decoding the fifthmessage digest, which is obtained by decoding the Y with the PubC, withthe PubU1 corresponds to the MD, and if (ii) a second decoded valueobtained by decoding the sixth message digest, which is obtained bydecoding the Y with the PubC, with the PubU2 corresponds to the MD, theprocessor 120 may determine or support another device to determine thefile as verified. In other words, the verification of the file may becompleted with three more steps.

The four steps of the verification above may be represented as theexpressions below.OP_MESSAGE==Hash[Enc _(PrivC)(Enc _(PrivU1)(MD)+Enc _(PrivU2)(MD))]Enc _(PrivU1)(MD)+EnC _(PrivU2)(MD)==Dec _(PubC)[Enc _(PrivC)(Enc_(PrivU1)(MD)+Enc _(PrivU2)(MD))]MD(=Hash[File])==Dec _(PubU1)[Enc _(PrivU1)(MD)]MD(=Hash[File])==Dec _(PubU2)[Enc _(PrivU2)(MD)]  <Expression 2>

On the other hand, in the serial signing process, the processor 120 maydetermine or support another device to determine the file as verifiedaccording to whether Hash[EncPrivC(EncPrivU2(EncPrivU1(MD)))], which isthe function value of a second encoded value acquired by encoding theoriginal message digest in sequence with the PrivU1, the PrivU2, and thePrivC, corresponds to the function value of the third message digest inthe OP message.

However, even in case that the function valueHash[EncPrivC(EncPrivU2(EncPrivU1(MD)))] of Z, which is the secondencoded value acquired by encoding the original message digest insequence with the PrivU1, the PrivU2, and the PrivC, corresponds to thefunction value of the third message digest in the OP message, ifDecPubU1(DecPubU2(DecPubC(EncPrivC(EncPrivU2(EncPrivU1(MD)))))) obtainedby decoding the Z in sequence with the PubC, the PubU2, and the PubU1corresponds to the MD, the processor 120 may determine or supportanother device to determine the file as verified. In other words, theverification of the file may be completed with three more steps.

The four steps of the verification above may be represented as theexpressions below.OP_MESSAGE==Hash[Enc _(PrivC)(Enc _(PrivU2)(Enc _(PrivU1)(MD)))]Enc _(PrivU2)(Enc _(PrivU1)(MD))==Dec _(PubC)[Enc _(PrivC)(Enc_(PrivU2)(Enc _(PrivU1)(MD)))]Enc _(PrivU1)(MD)==Dec _(PubU2)[Enc _(PrivU2)(Enc _(PrivU1)(MD))]MD(=Hash[File])==Dec _(PubU1)[Enc _(PrivU1)(MD)]<  Expression 3>

Next, said another example embodiment of responding to the verificationrequest in the authentication system using the distinct data structuremanaged by the server 100 is further explained.

On condition that the server 100 has acquired the authentication requestfor the file, and then has registered a first representative value orits processed value in the database, wherein the first representativevalue is generated by using a first specific value and its correspondingat least one neighboring value under one of the anchoring conditions,and wherein the first specific value is the function value of the resultacquired by encoding the specific message digest of the file with theprivate key of the first user, the private key of the second user, andthe private key of the server, if the verification request for the fileis acquired, if a second representative value or its processed value,generated by using the input data included in the verification request,corresponds to the first representative value or its processed valueregistered in the database, the processor 120 may determine or supportanother device to determine that the verification of the file iscompleted.

Herein, in the parallel signing process, the first specific value may bethe function value of EncPrivC(EncPrivU1(MD)+EncPrivU2(MD)), which isacquired by encoding a data group with the private key of the server,wherein the data group is comprised of the first encoded message digestgenerated by encoding the specific message digest with the private keyof the first user and the second encoded message digest generated byencoding the specific message digest with the private key of the seconduser.

In the serial signing process, the first specific value may be thefunction value of EncPrivC(EncPrivU2(EncPrivU1(MD))), which is acquiredby encoding the specific message digest in sequence with the private keyof the first user, the private key of the second user, and the privatekey of the server.

The present disclosure has an effect of guaranteeing fast service speedand reducing a transaction cost when providing a notary service for afile to perform authentication and verification in real-time byrecording authentication information in the blockchain of virtualcurrency.

The present disclosure has another effect of improving service speed andreducing the transaction cost by configuring a specific tree by usinginformation on the notary service and registering only a root value oran intermediate value of the specific tree with the blockchain insteadof registering all of the information on the notary service with theblockchain.

The present disclosure has still another effect of providing guaranteedintegrity of a database by performing the verification using thespecific tree generated in response to a verification request for thefile.

Meanwhile, the processor 120 may control a data flow among thecommunication part 110 and the other components. That is, the processor120 may control the communication part 110 and other components toperform their unique functions, by controlling the data flow among eachcomponent within the server 100.

The processor 120 may include hardware configuration of MPU (MicroProcessing Unit) or CPU (Central Processing Unit), cache memory, databus, etc. Additionally, OS and software configuration of applicationsthat achieve specific purposes may be further included.

The embodiments of the present disclosure as explained above can beimplemented in a form of executable program command through a variety ofcomputer means recordable to computer readable media. The computerreadable media may include solely or in combination, program commands,data files, and data structures. The program commands recorded to themedia may be components specially designed for the present disclosure ormay be usable to a skilled person in a field of computer software.Computer readable record media include magnetic media such as hard disk,floppy disk, and magnetic tape, optical media such as CD-ROM and DVD,magneto-optical media such as floptical disk and hardware devices suchas ROM, RAM, and flash memory specially designed to store and carry outprograms. Program commands include not only a machine language code madeby a compiler but also a high-level code that can be used by aninterpreter etc., which is executed by a computer. The aforementionedhardware devices can work as more than a software module to perform theaction of the present disclosure and they can do the same in theopposite case. The hardware devices may be combined with memory such asROM and RAM to store program commands and include a processor such asCPU or GPU composed to execute commands stored in the memory and alsoinclude a communication part for sending and receiving signals withexternal devices.

As seen above, the present disclosure has been explained by specificmatters such as detailed components, limited embodiments, and drawings.While the disclosure has been shown and described with respect to thepreferred embodiments, it, however, will be understood by those skilledin the art that various changes and modification may be made withoutdeparting from the spirit and scope of the disclosure as defined in thefollowing claims.

Accordingly, the thought of the present disclosure must not be confinedto the explained embodiments, and the following patent claims as well aseverything including variants equal or equivalent to the patent claimspertain to the category of the thought of the present disclosure.

What is claimed is:
 1. A method for verifying a file recorded by using anotary service, comprising steps of: (a) a server, if a verificationrequest for the file is acquired, identifying or supporting anotherdevice identify information on a specific tree related to the input dataincluded in the verification request and on its leaf nodes, referring orsupporting another device to refer to a certain transactionidentification (transaction ID) which corresponds to the information onthe identified specific tree, and acquiring or supporting another deviceto acquire an operation message (OP message) from the database byreferring to the certain transaction ID, on condition that the serverhas acquired a notary service request for the file, and then hasregistered a first representative value or its processed value in adatabase, wherein the first representative value is generated by using afirst specific value and its corresponding at least one neighboringvalue under one of anchoring conditions, and wherein the first specificvalue is a function value of a result acquired by encoding a specificmessage digest of the file with a private key of a first user, a privatekey of a second user, and a private key of the server; and (b) theserver, if a second representative value or its processed value,generated by using input data, corresponds to the first representativevalue or its processed value included in the OP message, determining orsupporting another device to determine that a verification of the fileis completed, wherein the second representative value is generated byusing a second specific value and its corresponding at least oneneighboring value, wherein the second specific value is a function valueof a result acquired by encoding the specific message digest of the fileextracted from the input data with a private key of a specific user andthe private key of the server, and wherein the second representativevalue is calculated by using the second specific value allocated to aspecific leaf node of the identified specific tree, and a function valueallocated to at least one of other leaf nodes corresponding to thespecific leaf node of the identified specific tree.
 2. The method ofclaim 1, wherein the first specific value is the function value of theresult acquired by encoding a data group with the private key of theserver, and wherein the data group is comprised of a first encodedmessage digest generated by encoding the specific message digest withthe private key of the first user, and a second encoded message digestgenerated by encoding the specific message digest with the private keyof the second user.
 3. The method of claim 1, wherein the first specificvalue is the function value of the result acquired by encoding thespecific message digest in sequence with the private key of the firstuser, the private key of the second user, and the private key of theserver.
 4. The method of claim 1, wherein, at the step of (a), the inputdata includes at least one of (i) the file, (ii) the specific messagedigest of the file, and (iii) an ID issued during the notary service forthe file.
 5. The method of claim 1, wherein (x1) the server calculatesor supports another device to calculate (i) the second specific valueand (ii) a function value allocated to a sibling node of the specificleaf node where the second specific value is allocated, to therebyacquire a resultant value, and then allocates or supports another deviceto allocate a function value of the resultant value to a parent node ofthe specific leaf node: (x2) the server, if the parent node is a rootnode of the identified specific tree, compares or supports anotherdevice to compare the function value or its processed value allocated tothe parent node, as the second representative value, with the firstrepresentative value or its processed value included in the OP messageretrieved from the database; and (x3) the server, if the parent node isnot the root node of the identified specific tree, repeats or supportsanother device to repeat the steps of (x1) to (x3) by using the functionvalue or its processed value allocated to the parent node as the secondspecific value.
 6. The method of claim 1, wherein the database is ablockchain of a virtual currency or the database is managed by theserver.
 7. A server for verifying a file recorded by using a notaryservice, comprising: a memory and a communication circuit for acquiringor supporting another device to acquire a verification request for thefile; and a processor for, if a verification request for the file isacquired, (I) performing a process of (I-1) identifying or supportinganother device identify information on a specific tree related to theinput data included in the verification request and on its leaf nodes,(I-2) referring or supporting another device to refer to a certaintransaction ID which corresponds to the information on the identifiedspecific tree, and (I-3) acquiring or supporting another device toacquire an OP message from the database by referring to the certaintransaction ID, on condition that the server has acquired a notaryservice request for the file, and then has registered a firstrepresentative value or its processed value in a database, wherein thefirst representative value is generated by using a first specific valueand its corresponding at least one neighboring value under one ofanchoring conditions, and wherein the first specific value is a functionvalue of a result acquired by encoding a specific message digest of thefile with a private key of a first user, a private key of a second user,and a private key of the server; and (II) if a second representativevalue or its processed value, generated by using input data, correspondsto the first representative value or its processed value included in theOP message, performing a process of determining or supporting anotherdevice to determine that a verification of the file is completed,wherein the second representative value is generated by using a secondspecific value and its corresponding at least one neighboring value,wherein the second specific value is a function value of a resultacquired by encoding the specific message digest of the file extractedfrom the input data with a private key of a specific user and theprivate key of the server, and wherein the second representative valueis calculated by using the second specific value allocated to a specificleaf node of the identified specific tree, and a function valueallocated to at least one of other leaf nodes corresponding to thespecific leaf node of the identified specific tree.
 8. The server ofclaim 7, wherein the first specific value is the function value of theresult acquired by encoding a data group with the private key of theserver, and wherein the data group is comprised of a first encodedmessage digest generated by encoding the specific message digest withthe private key of the first user, and a second encoded message digestgenerated by encoding the specific message digest with the private keyof the second user.
 9. The server of claim 7, wherein the first specificvalue is the function value of the result acquired by encoding thespecific message digest in sequence with the private key of the firstuser, the private key of the second user, and the private key of theserver.
 10. The server of claim 7, wherein, the input data includes atleast one of (i) the file, (ii) the specific message digest of the file,and (iii) an ID issued during the notary service for the file.